In modern wireless systems, such as, for example, cellular wireless access and fixed wireless access networks, there is a need for equipment, such as radio transceiver equipment in user equipment or at base stations or access points, which is economical to produce, while having high performance at radio frequencies. Increasingly high radio frequencies are being used as spectrum becomes scarce and demand for bandwidth increases. Furthermore, antenna systems are becoming increasingly sophisticated, often employing arrays of antenna elements to provide controlled beam shapes and/or MIMO (multiple input multiple output) transmission.
It is known to implement a radio transceiver having an array of antenna radiator elements, which may be formed as copper areas printed on a dielectric. A feed network may connect the antenna elements to transmit and receive chains of the transceiver. A ground plate may be provided, which may underlie the array of radiator elements, and which provides a radio frequency ground for the radiator elements.
In a cellular wireless networks, it is typically beneficial for an antenna array which is intended to transmit and/or receive radiation to and/or from a cell, for example to an angular sector, to be configured to minimise radiation into, and reception from, other cells. It may, in particular, be beneficial to provide a high so-called front-to-back ratio for the antenna, that is to say a high attenuation of radiation and/or reception in directions opposite to the direction of the main beam, in comparison with the gain of the main beam, since this radiation and/or reception may appear as interference to other cells. A high front-to-back ratio may improve the capacity of the system by reducing interference. However, conventional antenna array assemblies may achieve a limited front-to-back ratio.
It is an object of the invention to mitigate the problems of the prior art.